This invention relates to an internal combustion engine exhaust system and more particularly to an improved high performance exhaust system for an engine.
With internal combustion engines, the exhaust system is quite influential in affecting the performance of the engine. By appropriately sizing the length and cross-sectional flow area of the exhaust system, the engine power curve can be significantly altered. With multi-cylinder engines, the utilization of a common exhaust pipe for several cylinders can give rise to effects on the exhaust pulses from one cylinder to another. This is particularly true but not limited to two-cycle internal combustion engines because of there more frequent firing.
The exhaust pulses that exit the tailpipe end of the exhaust pipe are reflected back through the exhaust system to the exhaust ports of the engine. Thus, if the exhaust system is not properly designed, adverse performance can result. This problem is particularly relevant to certain types of vehicles which are compact in nature and which dictate from their configuration the configuration and length of the exhaust system.
In order to provide high performance, the exhaust system should be relatively short. However the use of short exhaust systems particularly when one exhaust pipe serves several cylinders, can result in sacrifices in power and performance at other engine speeds and loads. For example, a high speed exhaust system for a three-cylinder engine and particularly a two-cycle type engine can cause exhaust pulses that are transmitted back to other cylinders than that that is in the exhaust cycle. This can cause adverse effects on the scavenging. This is particularly a problem with two-cycle engines because of the relatively high degree of overlap between the scavenging port and the exhaust port, and the fact that these engines fire every crankshaft revolution. The same circumstances, however, also can apply to four-cycle engines.
It is, therefore, a principal object of this invention to provide an improved exhaust system for a multi-cylinder engine.
It is a further object of this invention to provide an improved exhaust system for a multi-cylinder engine that will improve the performance throughout the entire engine speed and load ranges.
It is a still further object of this invention to provide an improved and compact exhaust system for a multi-cylinder engine wherein pulse-back effects from one cylinder will not adversely affect other cylinders.